Biomedical subjects

E S Vitetta

Publications and source records attributed to E S Vitetta.

At least 91 records · Page 5Linked to original sources

PubMed1992

The antitumor activity of an anti-CD22 immunotoxin in SCID mice with disseminated Daudi lymphoma is enhanced by either an anti-CD19 antibody or an anti-CD19 immunotoxin.

The antitumor activities of immunotoxins (ITs) constructed with deglycosylated ricin A chain (dgA) and either anti-CD19 (HD37) or anti-CD22 (RFB4) monoclonal antibodies were compared in SCID mice with disseminated human Daudi lymphoma (SCID/Daudi). As reported previously, after intravenous injection with Daudi cells, SCID mice develop disseminated lymphoma, which infiltrates the vertebral column and causes paralysis of the hind legs before death. The mean paralysis time (MPT) has been taken as an end point in this tumor model. We have previously reported that early treatment of SCID/Daudi mice with RFB4 coupled to dgA prolongs the MPT in a manner consistent with the killing of 4 logs of tumor cells. In the present study, we show that HD37-dgA kills 2 logs of tumor cells. The lower potency of the HD37-dgA is consistent with its lower IC50 on Daudi cells in vitro. We further show that the antitumor activity of a mixture of HD37-dgA and RFB4-dgA is significantly enhanced in SCID/Daudi mice and is consistent with the killing in excess of 5 logs of tumor cells. However, identical enhancement was observed when a mixture of the RFB4-dgA and the HD37 antibody was administered. In contrast, enhancement was not observed when mice were injected with a mixture of the RFB4 antibody and the HD37-dgA. The results indicate that a "cocktail" of HD37 antibody and RFB4-dgA immunotoxin can have significant antitumor activity in this mouse model of lymphoma and suggest that combinations of particular antibodies and ITs may have cooperative antitumor activity.

Animals↗

PubMed1992

Memory T cells are anergic to the superantigen staphylococcal enterotoxin B.

We have used staphylococcal enterotoxin B (SEB) to study the role of naive and memory T cells in the induction of peripheral tolerance. After administration of SEB to mice, the numbers of naive and memory T cells increase, as does the proportion of memory T cells, which are unresponsive to further stimulation with SEB in vitro. In addition, memory T cells generated in response to conventional antigen, which proliferate and provide help to B cells in the presence of the conventional antigen, fail to respond to superantigen. Hence, memory T cells, in general, are anergized by SEB. These results suggest that SEB-induced activation and anergy reflect the combined responses of naive and memory T cells. The differential activation vs. anergy of naive and memory T cells by superantigen may be related to cytokine production and may play an important role in the etiology of autoimmune diseases or immunodeficiency diseases such as acquired immune deficiency syndrome.

Animals↗

PubMed1992

Induction of IL-4 secretion by the radiation leukemia virus (RadLV): role in autocrine growth stimulation of RadLV infected pre-leukemic cells.

Intrathymic inoculation of radiation-leukemia virus (RadLV) into C57BL/6 mice induces a population of pre-leukemic (PL) T cells which progress into clonal, mature thymic lymphomas after a latency period of 3 to 5 months. In order to understand how PL cells are retained in the thymus for a prolonged period of time we determined whether RadLV infected cells secrete and/or respond to a T-cell growth factor that may be involved in the long-term maintenance of a thymic PL-cell pool. We have previously found that in vitro proliferation of RadLV-infected PL cells is IL-4-dependent. Here we show that RadLV induces IL-4 secretion and IL-4 receptor (IL-4R) expression in normal thymic lymphocytes. RadLV-infected PL thymocytes express IL-4R and secrete IL-4. Their IL-4 secretion could be enhanced if incubated in the presence of RadLV and this enhancement was inhibited by anti-RadLV antibodies. Several RadLV-induced lymphoma lines secreted IL-4 and/or expressed IL-4R, but these features were not essential for their continuous growth. The results suggest that RadLV induces IL-4-dependent autocrine growth which maintains a population of PL T cells in the thymus. Transition from a PL state to overt thymic lymphoma involves emancipation of a PL cell from IL-4 dependency.

Animals↗

PubMed1992

Treatment of premalignancy: prevention of lymphoma in radiation leukemia virus-inoculated mice by cyclosporin A and immunotoxin.

Radiation leukemia virus (RadLV)-induced preleukemic (PL) latency is characterized by the appearance of virus-infected PL cells in the thymus. The survival of these PL cells is dependent upon autostimulation with interleukin 4 (IL-4). We have intervened prophylactically in RadLV-induced preleukemia by using cyclosporin-A (CSA), which inhibits IL-4 production, and an immunotoxin (ITx) that kills PL cells. CSA efficiently inhibited IL-4 secretion from RadLV-induced PL and leukemic cells, and its administration to PL mice caused a significant delay in their death. An ITx consisting of anti-RadLV glycoprotein-70 (gp70) antibody coupled to ricin A chain efficiently inhibited protein synthesis in virus-infected cells in vitro and, when injected into PL mice, also delayed their death. Combined treatment with CSA and ITx prevented 75% of the treated PL mice from developing lymphoma. These results show that the development of malignancy from a premalignant state can be averted by a combination of therapeutic modalities that decrease the size and growth rate of the premalignant cell population.

Animals↗

PubMed1992

Changes in expression of CD45R during the development of Th1 and Th2 cell lines.

Previous studies using anti-CD45R monoclonal antibodies (mAb) have shown that normal CD4+ T cells can be separated into virgin and memory cells based on their level of expression of CD45R. CD45Rhi (virgin) T cells secrete interleukin (IL)-2 whereas CD45Rlo (memory) T cells secrete both IL-2 and IL-4. In contrast to these results, studies using cultured T cell lines have shown that IL-2-secreting T helper cell type 1 (Th1) cells are CD45Rlo and IL-4-secreting Th2 cells are CD45Rhi. To resolve this discrepancy, and to determine how the Th1 and Th2 cell lines relate to memory CD45Rlo and virgin CD45Rhi CD4+ T cells, we have isolated CD45Rlo cells from alloantigen-primed mice and developed allospecific Th1 and Th2 cell lines. The lymphokines secreted by these lines were then evaluated. Our results show that as CD45Rlo T cells develop into in vitro cell lines which secrete IL-4, they become CD45Rhi. In contrast, CD45Rlo cells that develop into lines which secrete IL-2 maintain their CD45Rlo phenotype. Thus, although both Th1 and Th2 cells arise initially from CD45Rlo cells, Th2 cells become CD45Rhi during prolonged in vitro culture but, Th1 cells do not.

Animals↗

PubMed1992

The toxicity of chemically deglycosylated ricin A-chain in mice.

Tumor-reactive antibodies coupled to ricin or its A-chain (immunotoxins) have been used in rodents and humans to treat a variety of neoplastic diseases. Side-effects of such treatment include hepatotoxicity, vascular leak syndrome, myalgia and low grade fever. At high doses, severe toxicities include liver damage, pulmonary edema, aphasia, rhabdomyolysis and kidney failure. There have been a limited number of toxicologic studies on uncoupled ricin or its A-chain and none on deglycosylated A-chain. Since the latter has been utilized in "second generation" immunotoxins, the current studies were carried out to evaluate the toxicities induced by deglycosylated ricin A-chain (dgA) in mice. The administration of dgA to normal BALB/c mice causes early (24 h) weight loss and late (10 day) accumulation of ascites. These effects could be partially altered by changing the route of injection of dgA from i.v. to i.p. Thus, i.p. administration caused weight loss but not ascites, whereas i.v. administration caused both. Weight loss was associated with reduced fluid intake by the treated mice, and was not associated with increased levels of serum TNF-alpha. SCID mice injected with the same dose of dgA as normal BALB/c mice developed ascites, but it was of lesser severity, suggesting that a functional immune system, differences in microbial flora, or strain differences may be involved in the development of ascites.

Animals↗

PubMed1992

A CD4-derived peptide carrier blocks acute HIV-1 infection in vitro and binds to gp120 in the presence of Walter-Reed stage 1-6 HIV+ sera.

A peptide containing amino acid residues 41-84 of the CD4 molecule was synthesized and coupled through a thioether bond to human serum albumin. This conjugate bound to gp120 with an affinity that was half that of CD4 and blocked the HIV infection in vitro with an efficacy tenfold lower than that of CD4. More importantly, the CD4 peptide-human serum albumin conjugate could bind to gp120 in the presence of HIV+ sera from 18 Walter Reed stage 1-6 patients.

Acquired Immunodeficiency Syndrome↗

PubMed1992

IL-4-induced expression of germline gamma 1 transcripts in B cells following cognate interactions with T helper cells.

T cell-dependent B cell activation and the induction of isotype switching require antigen and direct contact with helper T (Th) cells. During activation, B cells can switch from the expression of IgM to that of IgG, IgE or IgA, depending on the lymphokines secreted by the Th cell with which they interact. Studies of lipopolysaccharide (LPS)-activated B cells have suggested that lymphokines regulate isotype switching via a transcriptional mechanism that increases the accessibility of downstream CH genes to a switch recombinase(s). To assess the roles of T cell contact and lymphokines in isotype switching, we have examined the accessibility model for the regulation of isotype switching to IgG1 in the context of cognate interactions between Th cells and normal B cells. We demonstrate that Th2 cells that secrete IL-4 can induce expression of germline gamma 1 transcripts in B cells. The steady-state level of germline gamma 1 transcripts induced by Th2 cells is enhanced as compared with the level induced by IL-4 alone or Il-4 and LPS also alters the relative usage of the germline gamma 1 transcription initiation sites. Enhanced expression of germline gamma 1 transcripts requires direct contact between T and B cells suggesting a role for T cell contact-mediated signals in regulating the accessibility of switch regions.

Animals↗

PubMed1992

The lineage relationship between virgin and memory B cells.

J11d is expressed on a variety of hemopoietic cells, including B cells. In previous studies, we have shown that B cells are heterogeneous with respect to their levels of J11d expression and that memory B cells are contained within the J11dlo B cell population. In this report, we have further examined the relationship between memory precursors and memory cells. We have found that the ability of J11dlo B cells from unprimed mice to respond to primary antigenic stimulation was generally low; the lowest response occurred following immunization with soluble antigen in vitro. Following adoptive transfer into irradiated mice and repeated stimulation of these mice with antigen, J11dlo cells generated memory responses which were similar to those generated by J11dlo memory cells obtained from primed mice. In contrast, J11dhi B cells from unprimed mice gave rise to both primary and memory responses, but the memory responses were lower than those generated by J11dlo cells. Although the expression of J11d on both J11dhi and J11dlo cells from unprimed mice decreased after adoptive transfer, J11dlo, as compared to J11dhi, virgin cells proliferated more rapidly. These results suggest that memory responses are elaborated predominantly from J11dlo virgin cells. Taken together with previous results, our studies indicate that, J11dlo B cells are different from J11dhi B cells. Hence, they are either memory precursors or are memory cells.

Animals↗

PubMed1991

Antitumor activity of Fab' and IgG-anti-CD22 immunotoxins in disseminated human B lymphoma grown in mice with severe combined immunodeficiency disease: effect on tumor cells in extranodal sites.

The antitumor effects of two anti-CD22 ricin A chain-containing immunotoxin (IT) constructs were compared in mice with severe combined immunodeficiency disease with human Daudi cell tumors (SCID-Daudi mice). SCID-Daudi mice develop disseminated lymphoma that clinically resembles African Burkitt's lymphoma, i.e., extranodal disease including infiltration of the vertebral column and spinal canal. In the absence of treatment, the mean survival time of SCID-Daudi mice was 45.9 +/- 4.3 days. The mice was given injections of a dose of IT equal to 40% of the 50% lethal dose. The ITs consisted of either IgG or Fab' fragments of mouse anti-CD22 antibody coupled to deglycosylated ricin A chain (dgA). Both ITs were potent and specific and inhibited protein synthesis in Daudi cells in vitro by 50% at concentrations of 1.2 x 10(-12) (IgG-dgA) and 1.3 x 10(-11) M (Fab'-dgA). When administered to mice beginning 1 day after inoculation with tumor cells, both ITs extended the mean survival time, to 87.2 +/- 18.9 days (IgG-dgA) or 57.9 +/- 3.8 days (Fab'-dgA). The latter represented the killing of 2 logs of Daudi cells, and the former 4 logs. IgG antibody alone killed 1 log of tumor cells. The IgG-dgA had an antitumor effect even when administered 20-23 days after tumor inoculation. Gross and histological examinations of IT-treated tumor-bearing mice showed a marked decrease in the number and size of neoplastic foci in both lymphoid organs and extranodal sites.

Animals↗

PubMed1991

Changes in expression of J11d on murine B cells during activation and generation of memory.

J11d is an antigen expressed on a variety of hemopoietic cells including B cells. In this report we describe the expression of J11d on functional subpopulations of B cells from adult mice of different ages or at different stages of an immune response. In addition we explore the relationship between the expression of J11d and that of other markers characteristic of memory B cells. Our results show that expression of J11d on B cells is related to the immunologic history of the host. Thus, J11d on B cells from normal mice is decreased as the mice age and are thereby exposed to environmental antigens. Down-regulation of J11d on B cells does not occur in germfree or nude mice but does occur when nude mice are reconstituted with T cells and/or are immunized. Since B cells expressing low levels of J11d accumulate following exposure to antigens, we also determined whether memory cells reside in the J11dlo cell population. To this end, we studied primed mice and found that expression of J11d on antigen-specific B cells increased during the first week after immunization and decreased thereafter. Increases in expression of J11d after activation also occurred in B cells stimulated with lipopolysaccharide (LPS) in vitro. However, antigen-specific B cells from long-term primed mice which expressed lower levels of J11d and antigen-specific receptors of higher affinity also expressed lower densities of sIgM and included most sIgG+ cells. Furthermore, these antigen-specific J11dlo B cells transferred a memory response, whereas J11dhi cells did not. Taken together, these data indicate that the level of expression of J11d on B cells distinguishes virgin (J11dhi) from memory (J11dlo) cells in mice.

Age Factors↗

PubMed1991

IL-4 down-regulates the expression of J11d on murine B cells.

T cell-derived IL-4 has many effects on murine B cells, including the up-regulation of class II antigens and the induction of isotype switching. The development of memory B cells and the decreased expression of J11d antigens on these cells are influenced by T cells. In this report, we determined whether the decreased expression of J11d can also be mediated by T cell-derived lymphokines and, in particular, IL-4. We found that IL-4 can down-regulate the expression of J11d on both large and small B cells, that this effect becomes significant after 48 hr of culture and occurs at doses of IL-4 that are similar to those required to up-regulate murine class II MHC antigens encoded by I-region alpha genes (IA). Anti-IL-4 antibody completely blocks this effect but IFN-gamma does not. Other lymphokines (IL-1, IL-2, IL-3, IL-5, IL-6) neither induce a decrease in J11d nor alter the ability of IL-4 to down-regulate J11d expression. The decrease in J11d expression on B cells is not due to a preferential survival of cells expressing lower levels of J11d, although IL-4 has a more pronounced effect on these B cells. Finally, the down-regulation of J11d and up-regulation of IA by IL-4 occurs on all inducible B cells.

Animals↗

PubMed1991

Cancer dormancy: studies of the murine BCL1 lymphoma.

Dormancy in the murine BCL1 lymphoma can be induced by several strategies including cytoreductive therapy of mice with large tumor burdens and challenge of allogeneic chimeric mice or idiotype-immunized mice with BCL1 tumor. Dormant tumor cells were isolated from the spleens of the chimeric mice and the majority were shown to be noncycling. In idiotype-immunized mice that had lost dormancy, tumor growth occurred at a relatively rapid rate. A proportion of idiotype-immunized mice that had lost dormancy spontaneously regressed and then again relapsed; in these mice, the serum antiidiotypic levels were inversely related to the tumor burden.

Animals↗

PubMed1991

The GLP large scale preparation of immunotoxins containing deglycosylated ricin A chain and a hindered disulfide bond.

The large scale preparation of two second generation immunotoxins containing murine monoclonal antibodies and deglycosylated ricin A chain is described. The procedure for the preparation of immunotoxins consists of the derivatization of antibody with SMPT and reduction of dgA with DTT followed by their reaction to establish a hindered interchain disulfide bond. The purification of the immunotoxin includes affinity chromatography on Blue-Sepharose to remove the free antibody and gel filtration on Sephacryl S-200HR to remove any high molecular weight material and free dgA. The two immunotoxins were prepared by GLP procedures and tested for yield, composition, purity, sterility and biological activity.

Antibodies, Monoclonal↗

PubMed1991

Evidence that natural murine soluble interleukin 4 receptors may act as transport proteins.

The present studies were undertaken to determine whether the interleukin 4 binding proteins (IL-4BPs) previously identified in the biological fluids of mice are soluble forms of IL-4Rs. We also studied the binding properties of IL-4BPs in order to gain insight into their physiological role in vivo. Affinity-purified IL-4BPs and recombinant soluble IL-4Rs generated similar one-dimensional (Cleveland) peptide maps after digestion with either Staphylococcus aureus V8 protease or trypsin, indicating structural similarities. Furthermore, a rat mAb directed against the murine IL-4Rs immunoprecipitated the IL-4BPs and completely inhibited binding of 125I-IL-4 to a purified preparation of IL-4BPs. Taken together these data indicate that the IL-4BPs are soluble IL-4Rs. At 4 degrees C the IL-4BPs competitively inhibited the binding of IL-4 to membrane IL-4Rs but their ability to prevent binding of IL-4 to cells at 37 degrees C, at the same concentrations, was significantly reduced. Kinetic binding studies of soluble IL-4BPs vs. membrane IL-4Rs disclosed important differences in their rates of dissociation from IL-4. Whereas dissociation at 4 degrees C was slow for both, dissociation of IL-4 from IL-BPs at 37 degrees C was considerably faster (t 1/2 of 2 min) than dissociation of IL-4 from membrane IL-4Rs (t 1/2 of approximately 69 min). Temperature-dependent changes in dissociation kinetics were reversible, and could not be accounted for by either inactivation of the IL-4BPs at 37 degrees C or receptor internalization. Additional experiments also demonstrated that when IL-4BPs bind to IL-4 at 37 degrees C, the IL-4/IL-4BPs complex can rapidly dissociate, allowing IL-4 to bind to membrane IL-4Rs. In addition, binding of IL-4 by the IL-4BPs protects IL-4 from proteolytic degradation. Taken together, these results suggest that the IL-4BPs are naturally occurring forms of soluble IL-4Rs and that some of their properties (fast dissociation kinetics and protection of IL-4 from proteolysis) are consistent with a potential role as carrier proteins for IL-4 in the circulation.

Animals↗

PubMed1991

Phase I immunotoxin trial in patients with B-cell lymphoma.

Fifteen patients with refractory B-cell lymphoma were treated in a Phase I dose escalation clinical trial with a highly potent immunotoxin consisting of the Fab' fragment of a monoclonal anti-CD22 antibody (RFB4) coupled to chemically deglycosylated ricin A chain. All patients had low, intermediate, or high grade non-Hodgkin's lymphoma. The immunotoxin was administered i.v. in two to six doses at 48-h intervals. The peak serum concentration and the t1/2 were not dose dependent among patients and averaged 1.3 micrograms/ml and 86 min, respectively. Three patients made antibody against A chain, and a fourth made antibody against both A chain and mouse immunoglobulin. Antibody responses were low (less than or equal to 85 micrograms/ml) in three patients and were not detected until 1 mo after treatment. The maximum tolerated dose of the immunotoxin was 75 mg/m2. Dose-related toxicities included vascular leak syndrome, fever, anorexia, and myalgia. Dose-limiting toxicities included pulmonary edema and/or effusion, expressive aphasia, and rhabdomyolysis (resulting in reversible kidney failure). There was no evidence of liver dysfunction. Partial responses were achieved in 38% of evaluable patients, and in those patients who had greater than 50% CD22+ tumor cells, 50% of the patients achieved a partial response. Clinical responses were not related to tumor grade and were generally transient, lasting between 1 and 4 mo.

Adult↗

PubMed1991

CD4 peptide-protein conjugates, but not recombinant human CD4, bind to recombinant gp120 from the human immunodeficiency virus in the presence of serum from AIDS patients.

Sera from human immunodeficiency virus-positive (HIV+; Walter Reed stage 6) individuals inhibit the interaction between recombinant human CD4 and recombinant gp120 from HIV (rCD4 and rgp120, respectively), thereby interfering with the ability of soluble rCD4 to block infection with HIV or rCD4-toxin conjugates to kill HIV-infected cells. In this report we demonstrate that the inhibitory activity of such sera is caused primarily by anti-gp120 antibodies that do not recognize the CD4 interaction site on gp120. To circumvent the problem of inhibition, we have generated a construct containing a peptide of CD4 (residues 41-84) conjugated to ovalbumin (three to five peptides per molecule). This multivalent conjugate binds to rgp120 and binding is not inhibited by antibodies in HIV+ sera.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Covalent binding of human alpha 2-macroglobulin to deglycosylated ricin A chain and its immunotoxins.

In this report we demonstrated that human alpha 2-macroglobulin (alpha 2M) reacts with deglycosylated ricin A chain (dgA) and its immunotoxins to form high molecular weight complexes (molecular mass approximately 800 kDa). This interaction has a t1/2 at 37 degrees C of 5 h and reaches completion at 24 h. Complexes of alpha 2M-dgA cannot be dissociated by guanidine, sodium dodecyl sulfate, or low pH, but can be partially dissociated by reducing agents, such as 2-mercaptoethanol in the presence of sodium dodecyl sulfate. This indicates that dgA or dgA-containing immunotoxins are bound to alpha 2M by disulfide bonds. The dgA-binding site on alpha 2M and the mechanism underlying its interaction with dgA are different from those described for proteases or methylamine. alpha 2M complexes do not bind to Blue-Sepharose 4B or anti-A chain-Sepharose, suggesting that the sites on dgA which bind Cibacron Blue or polyclonal anti-A chain antibodies are sterically blocked or modified by interaction with alpha 2M. The interaction of alpha 2M with dgA or its immunotoxins results in a 2- to 3-fold decrease in the activity of the dgA in both cell-free assays and cytotoxic assays. However 12 h after injection into mice, only 11% of immunotoxin was bound to alpha 2M because of the slow kinetics of the interaction versus the more rapid t1/2 of the immunotoxin in the circulation.

Animals↗